This research investigated the spatial and seasonal distributions of coccolithophorids in surface water of the northern South China Sea. The surveyes covered the period from April 2002 to July 2003 and 5 curises , 25 sampling station during four season. Abundance and taxa of coccolithophorids were studied by the scanning electron microscopy. A total of 28 species were identified. Emiliania huxleyi dominated in the surface water of the South China Sea, and has highest relative abundance (61.7%), then were Gephyrocapsa oceanica (16.0%), G. ericsonii (6.9%), Umbellosphaera irregularis (4.3%), and U. tenuis (4.9%). The cell density of coccolithophorids ranged from 1.98 to 127.43¡Ñ103 cells L-1 during study period. The highest average cell density of coccolithophorids occured in the winter (61.76¡Ó28.19¡Ñ103 cells L-1), lowest in the summer (8.44¡Ó1.67¡Ñ103 cells L-1). Coccolithophorids cell density in basin showed a positive linear relation with [NO2+NO3] and SRP (p<0.05). Principal component analysis indicates coccolithophorids could be identified as two separate groups: spring-winter and summer-autumn. E. huxleyi dominated in spring and winter, followed by G. oceanica. U. irregularis and U. tenuis dominated in the summer and autumn. Spectially, coccolithophorids communities differed in the shelf and the basin, with seasonal changes. In the shelf, E. huxleyi dominated in the spring, summer, and autumn, and followed by G. oceanica. G. oceanica dominated in the winter, and followed by E. huxleyi. In the basin, while E. huxleyi and G. oceanica dominated in the spring and winter, U. irregularis and U. tenuis dominated in the summer.